1. Field of the invention
This invention relates to a furnace for firing ceramic materials and having a crown element incorporating thermal and/or mechanical stress resisting means.
2. Description of the Prior Art
Known are, in particular from Italian Patents No. 27955 A.76 by this same applicant as well as from the first continuation in part thereto, presently pending for an independent patent grant filed under Ser. No. 25288 A/77, corresponding to U.S. Pat. No. 4,154,576, high thermal efficiency furnaces for firing ceramic materials, which are characterized in that they comprise a plurality of side-by-side chambers separated by partition walls, which chambers are defined at the top by a so-called crown wherethrough streams of hot combustion gases from the burners associated with such furnances--which open into the area defined by such crowns--are directed to the ceramic products to be cooked.
In such prior furnaces, the crowns are formed by so-called plates, having an upper face and lower face and being interconnected by partition ribs, whereby a number of channels, such as four, five, etc., are formed between the ribs. Such plates are supported at either ends by the furnace peripheral walls, and owing to the high thermal stress to which they are subjected, they may have a fairly small dimension between the furnace walls, thus imposing limitations to the furnance size. Between the plates, which are laid parallel to one another in side-by-side relationship and along the length of the furnace and tunnel forming it, suitable contoured patterns are provided for mutual engagement, especially at the plate mating areas.
Thus, it may be appreciated that with such plates, strength is solely provided by the plate structure, and that highly valuable materials must be used, which makes the plates a highly expensive item. Further, and as mentioned above, the plate width dimensions are restricted, which results in restrictions to the width dimension of the furnace itself.
Despite all these precautions, moreover, it is not unfrequent for the plates to develop cracks or break, which involves replacement and further aggravates the operating cost of the furnace, which must be deactivated.